They tested Google's ability to index and render JS, but not how well those sites ranked. I know as an SEO those results would look completely different. When you're creating content to monetize, the thought process is "why risk it?" with JS.
We have a customer who recently migrated from Wix to our headless CMS offering (which is WP/Next.js based) and their organic search traffic has improved 30% over the course of a month. But we believe this was largely due to CWV/speed improvements; impossible to parse out how much was due to Wix’s JS-based architecture itself.
